Bug 1: /voice off in TUI mode did not clear HERMES_VOICE_TTS,
leaving TTS stuck ON with no way to disable it (the voice.toggle
tts handler requires voice mode to be ON).
Bug 2: TUI status bar only showed 'voice on/off' without any
indication of whether TTS speech output is active, because the
frontend never tracked voiceTts state.
- tui_gateway/server.py: clear HERMES_VOICE_TTS when voice is turned off
- ui-tui/src/app/useMainApp.ts: add voiceTts state, thread setVoiceTts
through voice contexts, display [tts] in status bar
- ui-tui/src/app/slash/commands/session.ts: sync tts from voice.toggle response
- ui-tui/src/app/interfaces.ts: add setVoiceTts to all voice context interfaces